The invention relates to a method of and to a machine for simultaneously making two or more rods from fibrous material, especially from particles of natural, reconstituted and/or substitute tobacco. More particularly, the invention relates to improvements in methods and in machines of the type wherein a single flow of fibrous material is subdivided into several streams each of which is relieved of the surplus, if any, and is thereupon draped into a web of cigarette paper, imitation cork or other suitable wrapping material.
Machines which are capable of simultaneously making at least two rods of fibrous material are known for many years. Reference may be had, for example, to U.S. Pat. No. 4,463,767 which describes and shows a continuous twin rod making machine. The patent proposes to measure the quantity of tobacco particles in each stream prior to removal of the surplus, and to use the thus obtained signals for an adjustment of the partition which is employed to divide a single flow of tobacco particles into two discrete streams. This means that the position of one trimming device relative to the respective stream of tobacco particles can be different from the position of the other trimming device with respect to the corresponding tobacco stream. Consequently, even though the patented machine can ensure that the density of each stream matches or closely approximates a selected value, the characteristics of the rods which are obtained in such machines can deviate from each other. Furthermore, the quantity of surplus material in one of the streams can be different from the quantity of surplus tobacco in the other stream. On the other hand, it is desirable and advantageous to ensure that all characteristics of both streams, as well as of the rods which are obtained from such streams, be the same or should not appreciably deviate from each other.